#1  
Old 04-01-2012, 05:28 PM
mozzie's Avatar
mozzie (Peter)
Registered User

mozzie is offline
 
Join Date: Mar 2007
Location: moonee beach
Posts: 2,179
double stars in lepus

i finally had some viewing last night with clear days and cloud around 8pm every night you soon get sick off it...the clouds did come and go last night and the sky was soupy and thick seeing was a 6 out of 10...
the moon is filling up and giving us bright nights and when it's like this i love to look at double stars...i was using my 14"lx200 with mag of 102x and 209x i do have a 6.7mm around 550x it doesn't resolve the stars to well but you can see the split on some really close one's i didn't have that eyepiece last night it was in the house with my solar scope.i did manage to split down to 3.4" which i thought was pretty good and all the stars were in lepus and i was using sissy haas book on double stars....
i looked at around 16 pairs being able to see most but one or two where under 2" and i was unsure of seeing the split...
some highlights were:
s 476 :05h19.3m -18d31' 24.5" sep 2 nice 6th mag stars bright white and a third star beside and all 3 formed a straight line.
38 lep 05h20.4m -21d14' 4.1" sep pale yellow and white split at 209x
a lep 05h32.7m -17d49' a36" split with 2 faint 11mag companions at 209x a was surprised to see both these faint stars
y lep 05h44.5m -22d27' a fantastic pair a bright yellow and a brick red,what a surprise when first sighted..
i also tried to see sirius b the pup but was unable to spot again-one day i'll see it...
if you enjoy double stars have a look at the one's above.
Reply With Quote
  #2  
Old 07-01-2012, 01:33 PM
Suzy's Avatar
Suzy
Searching for Travolta...

Suzy is offline
 
Join Date: Jan 2010
Location: Brisbane, Australia.
Posts: 3,674
Mozzie!!!!

You've no idea how much you've just helped me out here.
Thank you!

The only star splits I've made so far have been A.Cent & G.Vela, and the last few days I've been eager to try and get a list together for some "easy splits", and I just didn't know where to start. So LesD kindly helped me out by explaining to me some arc seconds comparisons (I'm trying to get my head around arcs in an ep) by giving me a guide of A Cent being 5.4 arc seconds and A. Crucis abut 1.4 arc seconds (amongst some other harder comparisons). This to help me gauge a difficulty level. Then of course I've yet to work out magnification levels but he said I shouldn't have trouble splitting the 1 second arc mark at 300x in my 10". So I had some great help to go by with these and other tips he gave me, bless his heart.

I wanted something a little bit tighter than A. Cent. but easy enough still. So I was still needing to do a lot of work to find out which double stars lay a bit tighter in or around the same arc seconds to alpha cent. Your list looks do-able for me and I really enjoy spending the night observing within one constellation, so you have helped me even further.

Like you, fed up of constant bad weather and the nights when it's clear the moon is up, I decided to give double star observing a go.

Really enjoyed your report/descriptions.
Reply With Quote
  #3  
Old 07-01-2012, 08:24 PM
ngcles's Avatar
ngcles
The Observologist

ngcles is offline
 
Join Date: Dec 2006
Location: Billimari, NSW Central West
Posts: 1,569
Observations of Lepus pairs

Hi Peter, Suzy & All,

Very good and interesting observations of a several nice pairs. Just thought I'd add my own notes on Gamma Leporis for comparison.

Gamma Leporis is an interesting star from many points of view. It is a nearby star only 29 light-years away and the primary is roughly solar-type (F6 dwarf) about 1.25 solar masses and about twice as bright, while the companion is K-type and about 0.8 solar-masses. It is not clear whether they are a true pair or merely share a common proper motion. If they are physically bound, the true separation is about 870 AU. The two share a similar motion to Sirius and are possibly connected to the URSA major moving group -- a loose association of stars that are not gravitationally bound as a true cluster but share a probable common origin and similar metallicity, age and motion around the galaxy. Moving groups are not clusters, but are the low-mass counterparts the the high-mass O-B stellar associations.

Think of a moving group as a bunch of cars moving along the expressway together all travelling at about the same speed in the same direction and all having an approximately similar destination. Alternately for a cluster, think of a bunch of people on the bus on the expressway. Not only are they all moving in the same direction at the same speed, but they are stuck together and don't move away from each other. In the case of a true cluster, gravity binds them together and makes escape difficult (like the walls of the bus).

This was my eyepiece impression of Gamma Lep with 25cm at x138 in 1998:
x138 21' TF x181 17' TF. Mags 3.8 6.4 Sep 96.7 PA 350. A very wide and not very interesting pair with a mags disparity of 3 mags . Both yellowish, B is deeper, A is light/pale yellow. In PA 345, sep by nearly 2'.

There have been many interpretations of the colour of this pair over the years with some observers thinking the secondary member looked greenish (possible contrast effect). Pairs (particularly bright ones) can produce many interesting "perceived" colours. But that's the way I saw it anyway.

Colour is a highly subjective thing for visual observers ...


Best,

Les D
Reply With Quote
  #4  
Old 08-01-2012, 08:27 PM
mozzie's Avatar
mozzie (Peter)
Registered User

mozzie is offline
 
Join Date: Mar 2007
Location: moonee beach
Posts: 2,179
hi suzy,i do like to chase d/s and i can highly recommend sissy haas d/s for small telescopes around 2100 objects....i like you stay in one constellation well away from the bright moon and have a blast trying to split them..
Reply With Quote
  #5  
Old 08-01-2012, 08:31 PM
mozzie's Avatar
mozzie (Peter)
Registered User

mozzie is offline
 
Join Date: Mar 2007
Location: moonee beach
Posts: 2,179
Quote:
Originally Posted by ngcles View Post
Hi Peter, Suzy & All,

Very good and interesting observations of a several nice pairs. Just thought I'd add my own notes on Gamma Leporis for comparison.

Gamma Leporis is an interesting star from many points of view. It is a nearby star only 29 light-years away and the primary is roughly solar-type (F6 dwarf) about 1.25 solar masses and about twice as bright, while the companion is K-type and about 0.8 solar-masses. It is not clear whether they are a true pair or merely share a common proper motion. If they are physically bound, the true separation is about 870 AU. The two share a similar motion to Sirius and are possibly connected to the URSA major moving group -- a loose association of stars that are not gravitationally bound as a true cluster but share a probable common origin and similar metallicity, age and motion around the galaxy. Moving groups are not clusters, but are the low-mass counterparts the the high-mass O-B stellar associations.

Think of a moving group as a bunch of cars moving along the expressway together all travelling at about the same speed in the same direction and all having an approximately similar destination. Alternately for a cluster, think of a bunch of people on the bus on the expressway. Not only are they all moving in the same direction at the same speed, but they are stuck together and don't move away from each other. In the case of a true cluster, gravity binds them together and makes escape difficult (like the walls of the bus).

This was my eyepiece impression of Gamma Lep with 25cm at x138 in 1998:
x138 21' TF x181 17' TF. Mags 3.8 6.4 Sep 96.7 PA 350. A very wide and not very interesting pair with a mags disparity of 3 mags . Both yellowish, B is deeper, A is light/pale yellow. In PA 345, sep by nearly 2'.

There have been many interpretations of the colour of this pair over the years with some observers thinking the secondary member looked greenish (possible contrast effect). Pairs (particularly bright ones) can produce many interesting "perceived" colours. But that's the way I saw it anyway.

Colour is a highly subjective thing for visual observers ...


Best,

Les D
thanks les,as always love your reports.......i have one problem and it has been explained to me but i can't get my head around it p.a....and i use my sct and get completely confused which way to go to obtain that angle..
Reply With Quote
  #6  
Old 09-01-2012, 04:13 PM
ngcles's Avatar
ngcles
The Observologist

ngcles is offline
 
Join Date: Dec 2006
Location: Billimari, NSW Central West
Posts: 1,569
Position Angle

Hi Peter,

P.A (or position angle) is the number of degrees east of north the secondary star is from the primary. So PA 90 is due east, PA 180 is due south and PA 270 is due W.

So the distance in arc-seconds describes the size of the gap between the stars and PA describes the direction from the primary (brighter) and the secondary.

I don't know how you 'scope is mounted (eq of alt-az) but if it is an equatorial (assuming it is roughly aligned at least), your drive motors will move the 'scope in those 4 directions -- NSEW, so you can then estimate the PA. This of course is a bit trickier in an SCT used with a star diagonal and leaves you with a mirror-reversed image, but it can be done. It is harder still if the 'scope is mounted alt-az and its directions of motion don't line up with the cardinal directions. The best you can do (as you look through the ep) is to push it directly as possible toward the SCP. The direction new stars enter the field of view is approximately south and you can work the other directions out from there (taking into account the orientation of the view ie Mirror reversed, inverted, bot, etc etc.).

For extended objects like a galaxy, we only use the PA degrees between 0 and 179. A galaxy in PA 0 is lengthened (ie the major axis is elongated) exactly north-south. PA 45 is northeast-southwest, PA 90 is east-west etc etc. Obviously enough the angles between 179 and 359 are redundant and so not used.

Hope this helps.

Best,

Les D
Reply With Quote
  #7  
Old 10-01-2012, 03:47 PM
mozzie's Avatar
mozzie (Peter)
Registered User

mozzie is offline
 
Join Date: Mar 2007
Location: moonee beach
Posts: 2,179
thanks les

yes as you said it's harder with a sct in alt/az,that's me.....
i do try to use this p.a. as there is a close pair i would like to split.knowing where to look i conjunction with the brighter star and using the p.a to help me.
Reply With Quote
  #8  
Old 11-01-2012, 11:42 AM
blink138's Avatar
blink138 (Pat)
Registered User

blink138 is offline
 
Join Date: Aug 2009
Location: perth w.a.
Posts: 2,226
hello members just a quick one as there is a similar post on splitting sirius, for the first time at last new moon at christmas i saw rigel split... i honestly could not take my eyes off it
the massive glare of rigel then the tiniest bit of space and a tiny blue companion
what a contrast it was and i thought i wouldnt want to be on a planet orbiting the dwarf!
pat
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 05:08 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Advertisement
Celestron Australia
Advertisement
Bintel
Advertisement
OzScopes Authorised Dealer
Advertisement
Meade Australia
Advertisement
NexDome Observatories
Advertisement
Lunatico Astronomical
Advertisement
SkyWatcher Australia
Advertisement
Astronomy and Electronics Centre
Advertisement